Failed to enable unit: Unit file docker.service does not exist

~]# dnf install docker -y

~]# docker version
Emulate Docker CLI using podman. Create /etc/containers/nodocker to quiet msg.
Version:      3.2.3
API Version:  3.2.3
Go Version:   go1.15.14
Built:        Fri Sep 24 05:22:19 2021
OS/Arch:      linux/amd64

// 启动docker
~]# systemctl start docker
Failed to start docker.service: Unit docker.service not found.

~]# dnf remove podman -y

~]# dnf install -y yum-utils device-mapper-persistent-data lvm2

//官方源地址（比较慢）
~]# dnf config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
//阿里云
~]# dnf config-manager --add-repo http://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo
//清华大学源 
~]# dnf config-manager --add-repo https://mirrors.tuna.tsinghua.edu.cn/docker-ce/linux/centos/docker-ce.reposd

~]# dnf install docker-ce -y

~]# docker version
Client: Docker Engine - Community
 Version:           20.10.10
 API version:       1.41
 Go version:        go1.16.9
 Git commit:        b485636
 Built:             Mon Oct 25 07:42:56 2021
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
// 启动docker
~]#  systemctl start docker

// 设置开机自启
~]#  systemctl enable  docker
Created symlink /etc/systemd/system/multi-user.target.wants/docker.service → /usr/lib/systemd/system/docker.service.